1. Field of the Invention
The present invention relates generally to diagnostic systems for evaluating complex systems and subsystems, and in particular for diagnosing electronic, mechanical, and electromechanical subsystems.
2. State of the Art
Defense development is evolving more and more into a component integration, rather than a detailed design task. Commercial equipment, software, and third party objects (including software objects such as OLE, VCL, etc.) are being combined to create systems which previously would have been created as unique hardware and software design developments. This fundamental change in business approaches is due to several well known factors: 1) Availability of powerful, low cost commercial equipment and software; 2) the exit of many large scale manufacturers from the military marketplace; 3) reduced defense budgets; and 4) a general desire for acquisition reforms.
Diagnostic evaluation of integrated systems is complex. For example, diagnostic evaluation of the Apache AH64 helicopter is conventionally performed by a technician using a technical manual such as the U.S. Army Technical Manual 1-1520-238-T-3, Aviation Unit Maintenance Manual for Army AH64A Helicopter. To perform the diagnostic evaluation, the technician uses a Data Entry Keyboard (DEK) and a Heads Out Display (HOD) provided in the cockpit of the helicopter to look at the contents of certain memory locations in the onboard Fire Control Computer (FCC) of the helicopter. Subsystems in the helicopter are connected via a 1553 bus, and are configured so that they periodically put messages onto the 1553 bus that indicate their operational status. The FCC receives these status messages, and stores status information for each of the subsystems on helicopter. When a new status message is received for a specific subsystem, the FCC updates the stored status information for that subsystem using the new message, thus overwriting the old status information.
A technician can troubleshoot the helicopter by inspecting and interpreting the status information stored in the FCC. To do this, the technician selects a memory location in the FCC with the aid of the technical manual, keys in the FCC memory location using the DEK, and views the contents of that memory location as they appear on the HOD. The data appearing on the HOD is raw data corresponding to the selected portion of the subsystem status information stored in the FCC. This process is laborious because the technician can only look at a portion of the stored status information at one time, and must use the Technical Manual to interpret the raw data provided on the HOD to discern which FCC memory location to look at next, and to progressively determine which subsystem element or elements are causing specific problems indicated by fault codes in the raw data. The process of looking up and interpreting the contents of FCC memory locations until the helicopter is successfully diagnosed can take hours.
Other problems complicate this process. For example, when a technician is working on an aircraft whose systems have been updated and improved, he may be using an old manual that does not reflect these changes. Updated technical manuals may not even be available. Furthermore, the troubleshooting procedures outlined in the technical manuals are typically less effective when multiple faults are present in the helicopter, than when a single fault is present. This deficiency, especially when coupled with the slowness of troubleshooting using the technical manuals, is particularly egregious when the helicopter is used in active warfighting. For example, in a battlefield or battlefront situation, multiple faults due to battle damage are likely to be present, and when the helicopter is urgently needed back at the battlefront to continue fighting, the helicopter must be repaired as soon as possible. In some battle situations, a slow repair process could conceivably put one at a severe tactical disadvantage with respect to one's opponent.
Accordingly, a diagnostic troubleshooting aid is needed that is fast, accurate, relatively inexpensive, easily portable, and which can easily be adapted to not only identify and properly handle upgrades and modifications in the equipment it troubleshoots, but which can also be easily corrected and "taught" when it provides incorrect diagnoses.